1. Field of the Invention
An aspect of the present invention relates to at least one of a coordinate detection system, a coordinate detection method, and an information processing device.
2. Description of the Related Art
Conventionally, a coordinate detection system has been known that detects coordinates indicated by an indication tool such as an electronic pen on a coordinate input device and executes display of a handwritten character or the like.
In such a coordinate detection system, a variety of coordinate detection methods have been proposed that detect a position where a tip part of an indication tool contacts an input surface a coordinate input device. For example, Japanese Patent Application Publication No. 2004-038528 discloses an optical coordinate detection method wherein coordinates of a contact position of a tip part of an indication tool are detected in accordance with a process as described below.
Specifically, one-dimensional image sensors are placed at both edges of coordinate input device and detect revolution angles of two light emission points disposed on an indication tool with respect to a reference direction. Then, coordinates of such two light emission points are calculated based on detected revolution angles in accordance with a principle of triangulation. Moreover, coordinates of a tip part (that is, a contact position) are detected based on calculated coordinates of such two light emission points and known data of an indication tool (a distance between two light emission points or a distance from a light emission point to a tip part).
However, there is a problem as described below in a case of an optical coordinate detection method disclosed in Japanese Patent Application Publication No. 2004-038528.
For example, in a case where a light emission point is covered by a hand when the user holds an indication tool, it is not possible for one-dimensional image sensor part to detect the light emission point so that it is not possible to detect coordinates of a tip part. For this reason, it is necessary for a user to be careful in such a manner that, when an indication tool is held, a holding hand does not cover a light emission point in an image-taking direction of a one-dimensional image sensor part.
Furthermore, it is also considered that defocusing may be caused near a one-dimensional image sensor part or one light emission point may be out of an angle of field. For this reason, it is necessary for a user to be careful in such a manner that input of a handwritten character or the like is executed in an area that is appropriately away from a one-dimensional image sensor part.
Thus, it has not necessarily been considered that operability is good for a user in a case of a conventional optical coordinate detection system.